1. Field of the Invention
This invention relates to circuit breakers with ground fault protection, and more particularly, to small circuit breakers with toroidal sensing coils through which the power and neutral leads are passed to sense ground faults. Specifically, the invention is directed to bus bars for carrying higher currents through the sensing coils.
2. Background Information
There is increasing demand today to provide ground fault protection in circuit breakers, including the small circuit breakers typically used in residential and light industrial and commercial applications. The physical dimensions of the molded casings for such circuit breakers are constrained by the standardized openings in the enclosures and cabinets in which such circuit breakers are mounted. Thus, there is little room within the molded casing of such circuit breakers for adding the components necessary to provide the ground fault protection.
Common ground fault protection circuits include flat toroidal sensing coils through which the power and neutral leads pass to form transformers. Electronics connected to the sensing coils detect ground fault currents and energize a trip coil which trips the circuit breaker. The limited space available within the circuit breaker molded case restricts the size of the sensing coils that can be used. This in turn limits the size of the power and neutral leads which must pass through the central aperture of the toroidal sensing coils, and therefore limits the current rating of the circuit breaker. The problem is compounded in circuit breakers which provide neutral to ground fault protection as well as power lead to ground fault protection. These latter circuit breakers require two sensing coils in a commonly used ground fault protection circuit. Typically, these two flat toroidal coils have been mounted side by side within the circuit breaker molded housing which requires that the neutral and power leads bend 90 .degree. after passing through the coil in order to bridge the gap between the two sensing coils. This increases the overall thickness of the assembly, and hence the space required within the molded housing.
There is a known ground fault circuit breaker in which the two sensing coils are stacked in spaced relation with straight bus bars extending along the aligned axes through the coils. However, this makes the assembly wider.
There is a need therefore for a circuit breaker with ground fault protection having an increased current rating, yet of a physical size which can be contained within the standard size molded housing.